1. Field of the Invention
The present invention relates generally to rotors for electrical machines and more particularly to an improved design for the construction of slip rings for such machines and termination of electrical connections to the slip rings.
2. Description of the Related Art
In many electrical machines, a rotor includes an electromagnetic field generating coil which rotates with the rotor. In such machines, slip rings are typically provided as a part of the rotor assembly. The slip rings are means for connecting the field-generating coil to a source of electrical current.
Typical slip ring designs can present reliability improvement opportunities. For example, the two slip rings in a rotor are typically manufactured as a single assembly, with two wires extending from the assembly for connection to the field-generating coil. A first end of each wire is welded to a respective slip ring. A second end of each wire is welded to the wire which comprises the windings of the field-generating coil. The result is four interconnections between the field-generating coil and the slip rings. Although such designs have been honed to a relatively high degree of reliability, a reduction in the number of interconnections can improve reliability further. Also, the connections between the wires and the slip rings are challenging connections which, although reliable, can be made more reliable.
An additional area of potential improvement in prior art designs is in the cost of the slip ring assembly. A typical slip ring assembly is manufactured by the aforementioned welding of wires to the slip rings, followed by insert-molding of this subassembly in plastic. The resulting slip ring assembly is a fairly expensive part, exhibiting considerable opportunity for cost reduction.
Therefore, slip ring designs for electrical machine rotors which can provide improved reliability and reduced cost can provide advantages over the prior art.